Kenya's armed forces say the hostage standoff has nearly ended at the Westgate mall in Nairobi, where militants attacked shoppers with guns and grenades on Saturday, killing 68 people, including at least two Canadians.

"Most of the hostages have been released, and the Kenya Defence Forces has taken control of most parts of the building," Kenyan military spokesman Colonel Cyrus Oguna told the television station KTN. He did not say how many hostages had been held or freed.

Though a witness near the mall told Reuters that heavy and sustained gunfire was heard at the mall on Monday morning, suggesting a possible assault by Kenyan security forces.

Earlier Sunday, Kenyan officials said they expected the hostage-rescue operation to end "tonight."

Trucks had brought in a fresh contingent of soldiers from the Kenya Defence Forces early Sunday.

"Violent extremists continue to occupy Westgate Mall. Security services are there in full force," said the United States embassy in an emergency text message issued Sunday morning.

A large explosion rocked the mall earlier in the afternoon, followed by silence. It was by far the largest blast heard since the more than 30-hour siege began, according to witnesses. It came as Kenya's Red Cross rose the death toll from the attacks to 68.

Kenya's Disaster Operation Center said late Sunday that "this will end tonight. Our forces will prevail."

Israeli advisers were assisting Kenyan forces in formulating a strategy to flush out the militants still holed up inside Westgate, which is popular among tourists and expats.

2 Canadians died in attack

The first Canadian victim identified was confirmed by several federal departments as Annemarie Desloges, a 29-year-old diplomat who worked at the Canadian embassy. Desloges was previously posted in Delhi, and was off-duty shopping at the Kenyan capital's Westgate shopping centre on Saturday when the militants attacked with assault rifles and grenades.

Naguib Damji

Vancouver-area businessman Naguib Damji has been identified by family members as one of the Canadians killed in the mall attack in Kenya. (Courtesy Karima Damji/Facebook)

Desloges has worked for both Citizenship and Immigration Canada as well as the Canada Border Services Agency in Kenya, the offices confirmed in a joint statement Saturday night. She joined the CIC in 2006, then the foreign service in 2008.

Another Canadian who died in the attack at the upmarket shopping centre has been identified by Vancouver-area family members as Naguib Damji.

Niece Gulnaaz Lalji told CBC News that her uncle was having coffee at the mall when the attack began. After a large explosion, Damji suffered a cardiac event and died.

"Canada condemns in the strongest possible terms this cowardly, hateful act that apparently targeted innocent civilians who were simply out shopping," Prime Minister Stephen Harper said in extending his condolences to the victim's families.

Foreign Affairs Minister John Baird said he was stunned by the killings of Canadians in the militant attack. The al-Qaeda-linked Somali group al-Shabaab has claimed responsibility for the assault, which reportedly targeted non-Muslims.

"That people could be gunned down in broad daylight in a shopping mall on a weekend is just a tremendous tragedy," Baird said from London, Ont. "And obviously when you have someone who is serving their country abroad, it’s quite devastating."

10 to 15 gunmen still inside

Freelance journalist James Reinl told CBC News from Nairobi it's believed that "something like 10, 15 gunmen" remain inside the building with hostages.

"We understand that there is a final standoff where the security services are ready to launch a raid on the final number of gunmen who are in the building with hostages," Reinl said. "We don't know how many civilians are inside, exactly, particularly because there will be many hiding in different parts of the building."

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Annemarie Desloges, left, was killed when Somali militants attacked an upscale mall in Nairobi, Kenya on Saturday. Her husband Robert Munk, right, was also injured. (Facebook)

Kenya's interior cabinet secretary Joseph Lenku said that Kenyan forces have control of the security cameras inside the mall. Combined military and police forces have surrounded the building.

The President of Kenya, Uhuru Kenyatta, addressed the nation on Sunday just a few miles away from Westgate, where Kenyan military forces continued to engage with sporadic gun battles with the hostage-takers. He noted that he also had been affected personally by the tragedy.

"My nephew and his fiancée were among those who died in the attack," he said. "Many of us have lost loved ones. Let us mourn them all as one nation."

High Commission of Canada in Nairobi closed

The High Commission of Canada in Nairobi will be closed Monday.

Canadians requiring assistance should call the office or the Emergency Watch and Response Centre in Ottawa.

Kenyatta expressed confidence that Kenyan security forces would be able to "successfully neutralize the terrorists" that he said were currently cornered in the building. He said the militants were reported to be both male and female, though that could not confirmed.

"They shall not get away with their despicable and beastly acts," he said. "Like the cowardly perpetrators now cornered in the building, we will punish the masterminds swiftly and, indeed, very painfully."

U.S. President Barack Obama phoned Kenyatta to express the United States' condolences after the attack, with Obama affirming his country's efforts to bring down al-Shabaab.

About 1,000 civilians rescued

About 1,000 people have been rescued so far from the Westgate mall. Among the lucky ones were the 22 staff and patients at Dr. Sunil Sachdeva's dental clinic on the mall's fourth floor.

Sachdeva was treating patients around 1 p.m. Saturday when he heard the first shots ring out.
 

American survivor

American Sara Head spoke to CBC News about what it was like to hide from gunmen at the Westgate shopping centre in Nairobi. Read her story here.

Sachdeva told CBC News he ushered his patients and their parents in the reception room into a corridor and locked it down, muting phones and switching off the lights.

"And we just literally held our breaths and waited," he said.

Peeping from the windows, Sachdeva said he and his patients saw fleeing shoppers "sprayed" with gunfire as they tried to run outside. Some ran, then collapsed.

When Kenyan military arrived to help his staff and patients escape, Sachdeva said he took time to assess the carnage around him. There were spent shells littering the ground, as well as an unexploded grenade, he said.

"When I looked around the rooftop, I counted about 12 bodies, all covered with red sheets," he said, his voice breaking with emotion.

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A soldier from the Kenya Defence Forces arrives at the Westgate Shopping Centre in Nairobi. Kenyan security forces are locked in a stand-off with gunmen in the upmarket mall. (Thomas Mukoya/Reuters)

"We formed kind of a human chain guiding these people and taking care of the injured and taking care of people who were fainting ... A lot of people just came out and fell on their knees and broke down crying."

Kenya's presidential office said that one of the attackers was arrested on Saturday and died after suffering from bullet wounds.

United Nations Security Council issued a statement on Saturday condemning what they described as a terrorist attack in Nairobi.

"The members of the Security Council reaffirm that terrorism in all its forms and manifestations constitutes one of the most serious threats to international peace and security, and that any acts of terrorism are criminal and unjustifiable, regardless of their motivation, wherever, whenever and by whomsoever committed," the statement reads.

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An aerial view and map of the Westgate shopping centre in Nairobi, where an attack killed at least 59 people on Saturday. (Google/CBC News)

With files from Reuters and The Associated Press